How Much is Enough?

The dietary recommendations for calcium and vitamin D have changed. Having too much can be risky, but debate abounds.

Vitamin D has been one of the most talked about vitamins in recent years, and many scientists and physicians have recommended high intakes to ward off certain diseases. And calcium supplements have been recommended for older women to help protect their bones from osteoporosis. Now, after studying decades of research and reviewing over 1,000 studies, the Institute of Medicine (IOM) has decided that most people get enough vitamin D and calcium without supplements.

The new recommendations for vitamin D intake are 600 international units (IUs) a day from age 1 to age 70 and 800 IUs a day for those 71 years and older. This is an increase from the 200 to 600 IUs (depending on age) previously recommended by the IOM, but much less than the 1,000 to 2,000 IUs that some scientists wanted to see.

Bone health is the most well-established role of vitamin D and the primary function of calcium in the body. They work together to strengthen bones. Vitamin D makes calcium available in the blood surrounding the bones. As the mineral is deposited into the bones, the bones grow stronger and denser.

The IOM, a branch of the National Academy of Sciences, set new Dietary Reference Intakes (DRIs) for vitamin D, raising the recommended amount from the values set in 1997. The new values for both vitamin D and calcium are based on better studies and much more information than was available when the values for these nutrients were first set in 1997.

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The new recommendations for vitamin D intake are 600 international units (IUs) a day from age 1 to age 70 and 800 IUs a day for those 71 years and older. This is an increase from the 200 to 600 IUs (depending on age) previously recommended by the IOM, but much less than the 1,000 to 2,000 IUs that some scientists wanted to see. The report set these levels as the "recommended dietary allowance" (RDA) for vitamin D.

Some were disappointed in the IOM’s report such as Dr. Cedric Garland of the University of California, San Diego, who called the report a "stunning disappointment." He believes the risk of colon cancer could be greatly reduced in people who consume more vitamin D. Others such as Dr. Joann Manson of Harvard Medical School praised the report saying, "More is not necessarily better."

There are few dietary sources of vitamin D, and it is difficult to meet the recommended intake with food alone. Most of the vitamin D consumed comes from cereal or milk that is fortified with vitamin D, eggs, liver, butter, and some fatty fish like salmon and tuna. However, the human body makes its own vitamin D when the skin is exposed to sunlight for 10 to 15 minutes a few times a week.

Adolescent girls may be the only group not consuming enough calcium, the panel found. Older women, may be putting themselves at risk for kidney stones by taking supplemental calcium.

Despite headlines over the past few years claiming that most people don’t get enough vitamin D, according to the IOM report the average American has enough vitamin D circulating in his or her blood.

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One of the problems is that there is no set standard for what are sufficient and deficient vitamin D levels. A blood sample one lab finds deficient may be sufficient at another. The report says that 20 to 30 nanograms is sufficient for bone health, yet many labs label people as deficient in vitamin D if blood levels are below 30 nanograms. Research on the claims that vitamin D prevents a number of illnesses (such as cancer, heart disease, autoimmune diseases, and diabetes) has yielded conflicting and mixed results and need to be studied further.

The expert panel also looked at national data on diets and determined that most people get enough calcium from the foods they eat, so recommendations did not change significantly. The RDA was set at 1,300 mg a day for children from age 9 to age 18, 1000 mg a day for ages 19 to 70,and 1,200 mg a day for women 51 years and older.

Adolescent girls may be the only group not consuming enough calcium, the panel found. Older women, may be putting themselves at risk for kidney stones by taking supplemental calcium. The panel also found some evidence that excessive calcium may raise the risk for heart disease.